Fluid overload detection is difficult, from administering excessive fluids and or pathologic conditions. Fluid overload leads to increased morbidity and mortality. While fluid administration is paramount for maintaining tissue perfusion and preventing hemodynamic collapse in the hemorrhaging patients, excessive fluid administration results in decreased organ perfusion, acidosis, coagulopathy, and increased mortality [6, 18, 19]. Studies dating back to World War II have emphasized the importance of restricting fluid therapy prior to definitive surgical control [20]. Nonetheless, fluid resuscitation remains largely unguided due to inadequate hemodynamic monitoring and decision-support mechanisms [9]. Standard vital sign monitoring fails to detect euvolemia or hypervolemia during resuscitation, resulting in unguided, excessive fluid administration. Further, invasive monitoring is often not feasible. This leaves a critical need for a point-of-care monitor for real-time guided fluid resuscitation. Similarly, patients with congestive heart failure and renal failure often have fluid overload, leading to repeat hospitalizations [21]. Often this is not detected until after patients have symptomatic pulmonary edema and shortness of breath. Therefore there is an unmet need for a non-invasive volume status monitor in the outpatient setting to detect fluid overload in patients with cardiac and renal failure prior to the development of symptoms and need for hospitalization.
Further, hemorrhagic shock remains the leading preventable cause of death in the casualty care setting [2, 3]. Survival is contingent upon early recognition of hemorrhage, appropriate triage, and goal-directed transfusion therapy [4, 5]. Timely damage control surgery (DCS) and restrictive fluid resuscitation (RFR) have been shown to significantly improve mortality [6]. However, recognition of subclinical hemorrhage and proper fluid resuscitation has remained elusive, resulting in delayed triage and poor management of patients with acute blood loss [7].
Subclinical and ongoing blood loss is difficult to detect. Often, continuous occult bleeding is not recognized until the onset of hemorrhagic shock and hemodynamic collapse, particularly in young, healthy patients with good compensatory mechanisms [8, 9]. Unrecognized hemorrhage leads to delayed triage and DCS, resulting in preventable end-organ damage [10-12]. Standard vital sign monitoring, including heart rate and blood pressure, fails to detect hemorrhage prior to end-organ damage [7, 13]. Arterial-based methods such as pulse pressure variation (PPV), stroke volume variation (SVV), and plethysmographic wave respiratory variation can only predict fluid responsiveness but do not directly measure volume status [14, 15]. Further, PPV and SVV depend on changes in heart-lung interactions via mechanical ventilation for detecting hypovolemia [14, 16]. This critical limitation renders arterial-based monitors ineffective for detecting hypovolemia in the spontaneously breathing patient [17]. There is an acute unmet need for a point of care monitor that can measure volume status in patients, detect early subclinical hemorrhage and warn of impending hemodynamic collapse. Optimal patient care and measurements of volume status is particularly challenging in the casualty care, emergency response or rural setting. The casualty care or rural setting poses several unique challenges—austere environments, limited access to healthcare providers, ineffective monitoring devices, and lack of remote monitoring. There is a critical need for a rugged, real-time mobile monitoring and decision support mechanisms to improve survival in these environments. Therefore, there is a critical unmet need for a cost effective point of care device to assess the fluid status in patients for hemorrhage detection, goal-directed resuscitation, dehydration, fluid overload, and appropriate triage to improve mortality and need for hospitalization.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.